Sodium chloride (‘salt’) is used throughout the food industry to impart a ‘salty’ flavour to foods and beverages. However, sodium chloride is also known to cause an increase in blood pressure in mammals leading to a variety of cardiovascular diseases. To reduce its use, there is a need for compounds that do not elevate blood pressure yet can impart a ‘salty’ flavour in foods and beverages.
Certain protein hydrolysates, including fish protein enzymatic hydrolysates, are known to possess flavour potentiating activity and to have a flavour activity qualitatively resembling that of monosodium glutamate (MSG). However, the taste profiles and potentiating activities of protein hydrolysates, including fish protein hydrolysates, cannot be predicted a priori since the specific taste profiles and potentiating activities depend heavily on the particular species from which the protein is obtained and may depend on the method of hydrolysis.
Katsuobushi is a flavourant derived from dried bonito (tuna-like fish) used in traditional Japanese cuisine. Katsuobushi is produced from bonito muscle that has been boiled, smoked and fermented. It is known to have the ‘umami’ taste, which is a separate taste category from the classic basic taste categories of ‘sweet’, ‘sour’, ‘bitter’ and ‘salty’.
Katsuobushi oligopeptide (KO) is a hydrolysate prepared by enzymatic digestion of katsuobushi with thermolysin. KO has blood pressure lowering properties because it contains peptides that inhibit the activity of angiotensin I-converting enzyme (ACE). In Japan, a soup containing KO has been approved as a “Food for Specific Health Use” (Fujita, et al. (2001) “Effects of an ACE-inhibitory agent, katsuobushi oligopeptide, in the spontaneously hypertensive rat and in borderline and mildly hypertensive subjects” Nutrition Research 21:1149-1158).
KO was developed specifically for its ACE inhibitory activity for application in functional foods. However, it could not be anticipated that KO would have the additional beneficial attribute of a salt-replacement substance.